Method of connecting thin plates

ABSTRACT

A method and apparatus for performing the method, for connecting stacked thin plates 4, 5 (in particular sheet-metal plates) or plate sections, according to which stacked flat parts 10, 11 of both plates are first deep drawn together with one another, after which the bottom area of the deep-drawn flat parts is swaged wider, and wherein the radial expansion of the bottom area of these deep-drawn flat parts is limited, as a result of which a plastic deformation of the material of the plate takes place, particularly in the peripheral area, so that a connection point is created. By means of a crimp 17 present in the peripheral area of the bottom 16 of the blind opening 3 of the die 2, the swaged material flows into itself at the point that is to be connected, and hence the clinching strength, is improved.

BACKGROUND OF THE INVENTION

This invention is based on a method for connecting thin plates stackedon one another and on an apparatus for performing this method as definedhereinafter.

In a known method and apparatus of this kind (German OffenlegungsschriftNo. 31 06 313), the identical generally flat parts stacked on oneanother are deep drawn over a relatively long path, after which anenlarged stretched area is formed on the side via a lateral extrusion ordrawing compression, mechanically chaining the thin plates togethersomewhat as a rivet would do. To gain sufficient underlying support fora die for the deep drawing, on the one hand, and on the other hand tohave enough space available during this same swaging operation for thematerial that is spread out by being swaged, the bottom die has twooutwardly pivotable parts, which are displaced by the material as itflows radially outward during the swaging operation. At the moment inthe operation when this pivoting is completed, the deep drawing hasalready ended, so the bottom die parts are no longer required for deepdrawing.

This known technique has the following disadvantages: first, arelatively large "connector button" is created; second, a bottom dietool of this kind, with pivotable parts, can have no more than arelatively short service life given the required high pressure load;third, this apparatus is relatively expensive; fourth, because of theyielding pivoting parts the deep drawing is not of uniform quality, eventhough these parts are pulled counter to one another when the load isfirst imposed; and fifth, this bottom die tool, with its moving parts,is extraordinarily vulnerable to dirt, since when chips are produced,which is unavoidable in metal working, the resiliently supportedpivoting parts can easily become stuck in the open position, and afterthat the tool could no longer function properly.

Another method and apparatus for another known type (German Pat. No. 1942 411) combines a stamping operation and a deep drawing operation. Thediameters of the die opening and of the shaping die for the stampingoperation correspond to one another, and interspaces appropriate for thedeep drawing operation are provided in the form of recesses; asubstantial difference from the generic type initially described aboveis that the edge of the lower sheet-metal layer is upset radially inwardduring the compression operation. Aside from the disadvantage that withthis technique the connection is no longer liquid-tight or gas-tight, italso requires two separate operations, which are also handled in thepress apparatus. Not least, a stamping operation means that aconsiderable weakening of the material connection takes place.

OBJECT AND SUMMARY OF THE INVENTION

The method according to the invention has the advantage that a solidconnection is made in a single operation, that the "connecting cam" ofthis connection protrudes relatively slightly beyond the surface of theplate, that tool failure due to dirt or wear is impossible, and that thetools can be manufactured extremely inexpensively.

In one embodiment of the invention, there is a continuous crimp in theperipheral area of the bottom of the blind opening. As a result, betterflowing of the swaged material into itself at the points that are to beconnected is attained, since excess material can be caused to flow outof the way.

According to the invention, metal sheets or bands can be used as thethin plates, and the connection according to the invention also appliesto metal sheets with bands. In addition to this connection of metalsheets, connections between nonmetallic plates or of nonmetallic platesand metal plates are also encompassed by the invention.

The invention will be better understood and further objects andadvantages thereof will become more apparent from the ensuing detaileddescription of preferred embodiments taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 show a first exemplary embodiment in two variants:

FIG. 1 is a longitudinal section taken through a first tool according tothe invention, seen prior to the operation but with metal sheetsinserted in place;

FIG. 2 shows a tool position after the end of the deep drawingoperation;

FIG. 3 shows a tool position after the end of the swaging operation;

FIG. 4 is a longitudinal section taken through the second variant of thetool in a position corresponding to the tool position shown in FIG. 3;and

FIGS. 5 and 6 shows a further exemplary embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawing, only the actual manufacturing tool is shown. In FIGS.1-4, the first exemplary embodiment is shown in three working positions.Naturally for the sake of completeness the pressing apparatus is alsopart of the invention; this may be embodied in the most various ways,and by means of it, in order to make the connection according to theinvention, an upper die 1 must be movable back and forth in thedirection of a die 2. The die 2 is inserted fixedly into the pressingapparatus (not shown) and has a cylindrical flat blind bore 3 ofcircular cross section. Onto this die 2, which is thus embodied as abottom die, a lower plate 4 and an upper plate 5 which are to be joinedtogether therewith are placed. These plates 4 and 5, in this exemplaryembodiment, are sheet-metal plates.

The shaping die 1 has a holder shaft 6 and a coaxially disposed workingtang 7 of smaller diameter, so that a shoulder 8 is formed.

In FIG. 2, the first part of the operation is shown, that is, the deepdrawing is ended, in which the working tang 7 has drawn the flat part ofthe two plates 4 and 5 that precedes its free end face 9 into the blindbore. At the stretched connections 10 and 11 between the metal sheets,which remain in their original position, and the deep-drawn flat parts,thinning of the material takes place; however, the cup-shaped recessdoes not yet bring about an interlocking of the metal sheets 4 and 5.

In FIG. 3, the shaping die 1 is shown in its final position, namelyafter the swaging of the deep-drawn flat parts. In this position, theshoulder 8 rests on the surface of he metal sheet 5. The flat partsfacing the end face 9 are highly compressed, and this operation causesthe swaged material to effectively flow radially outward. The blind bore3 is filled up completely, and at the same time a material-strengtheningor densification of the deformed material has taken place. Because ofthe swaging effect, the upper flat part 13 has been radially stretchedout to such an extent that it extends behind the deep-drawing opening 14of the lower metal sheet 4. As a result of the strong forces ofdeformation, an extremely solid form-fitting connection is also attainedbecause the material is caused to flow radially outward as noted above.To prevent a notching effect, which could possibly cause tearing off ofthe upper flat part 13 from the plate 5, the face end 9 of the workingtang 7 is embodied as basket-shaped. Between the two plates 4 and 5,slightly rounded contact faces are created automatically in any caseduring the deep drawing operation.

To expel the workpiece, all that needs to be done now is to withdraw theshaping die in an upward direction; after that, the molded deformed areacan now be raised slightly out of the blind bore, which has smoothboundary walls in the direction of movement.

In the second exemplary embodiment of a tool shown in FIG. 4, theworking position of which corresponds to that shown in FIG. 3, acontinuous crimp 17 of wedge-shaped cross section is present in theperipheral area of the bottom 16 of the blind bore 3, into which thematerial positively displaced by the working tang 7 is also swaged, sothat a more pronounced flowing of material can take place as by the flowlines. Since it is possible to cause an increased area of interlockingbetween the juxtaposed sheets as well as a radial flow of material ineach sheet, a firmer connection is effected than in the first variant.

In the same manner, instead of two metal sheets shown by way of example,a larger number of thin plates stack on top of one another can also bejoined together. The approximate resultant course of the surfacescontacting one another in the case of four plates is indicated in FIG. 4by two broken lines. The important factor is that in the shaping die andin the blind bore of the bottom die, the wall surfaces facing oneanother extend parallel and in the deep drawing direction, so as toenable easy removal of the interconnected plates from the tool. Thecross section of the upper die and the corresponding blind opening maybe oval, polygonal or of some other shape. It is also conceivable forthe blind opening to be embodied as a groove, in which for the length ofthe groove, or in individual segments, a connection line or connectionpoints are produced by a suitably embodied shaping die, with the actualswaged connections being created between the side walls of the grooveand the shaping die walls facing those walls.

In the second exemplary embodiment shown in FIGS. 5 and 6, this clinchedconnection is effected via the nip between the two rollers, with theplates 4 and 5 being compressed as they are drawn through the rollerpass. On the running face 18 of the upper roller 19, an arcuateprojection formed as a strip 21 serves as the shaping die is provided,while on the lower roller 22 there is provided a groove 23 which iscomplemental to the strip 21 and this serves as the blind opening. Theproduction process, divided into the operations of deep drawing andswaging, is attained here in the form of a gentle transition as theplates 4 and 5 are drawn through the pass between rollers 19 and 22,with the deep drawing operation taking place before the compressionpassage through the rollers and the swaging operating then beingcompleted in this densely compressed area of the tightest passage. As aresult, it is also possible to produce relatively long seams, which mayeven lend the plates flexural strength, if that is desired.

According to the invention, it is also possible to use only one rolleron which the shaping dies are provided and which cooperates with a flatbottom die face, in which the blind openings are disposed. In such anapparatus, the plates 4 and 5 would be at rest, while the roller wouldroll over the plates.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

What is claimed and desired to be secured by Letters Patent of theUnited States is:
 1. A method for connecting stackable sheet-metalplates by a deep drawing and swaging operation by passing said sheetmetal plates between a pair of upper and lower die elements at least oneof which has an extension with an end face and a shoulder zone with theother having a blind opening having a closed end to thereby create aninterlock between said plates, the steps of:introducing said sheet-metalplates between said upper and lower die elements; applying a force onsaid upper die element to achieve a deformation of the said sheet-metalplates whereby a lower one of said plates is pressed into said blindopening and against said closed end thereof and a portion of an upperone of said sheet-metal plates enters a recess formed in said lowerplate, continuing to apply force onto said plates to bring about swagingand further deformation of the sheet-metal plates; preventing radialexpansion of said upper and lower plates within said blind opening,applying further force to said upper die element to bring aboutengagement of said shoulder zone of said upper die element into contactwith said upper one of said sheet-metal plates to thereby prevent anoutward flow of the metal from the blind opening and cause radial flowof the metal between said upper die element and the closed end of theblind opening of said lower die element to interlock the deformedportions of the plates adjacent the closed end of the blind opening ofsaid bottom die, whereby a seam connection between said sheet-metalplates is created; and said seam connection has a peripheral face whichextends in the deep drawing direction.
 2. A method as defined by claim1, wherein that after the swaging operation the surface of the bottomarea of the sheet-metal plates is located outside the plate plane formedby the underside of the stacked plates.